Highly sensitive relay with permanent magnet and shunt



Dec- 3 1963 R. Mosl-:R ETAL 3,113,251

HIGHLY SENSITIVE RELAY WITH PERMANENT MAGNET AND SHUNT Filed Feb. 2, 1962 2 sheets-sheet 1 fg/ FZgf-Z @a/44 3v 5 F M43P Y N 5 1 6 1 Fr\ Je a 1/\/ 2/\ a Z/ 5 e] Si 4 3 51 4 3 fgf' E I l .a g il Dec 3 1963 R. MosER ETAL 3,113,251

- HIGHLY SENSITIVE RELAY WITH PERMANENT MAGNET AND SHUNT 2 Sheets-Sheet 2 Filed Feb. 2, 1962 WI Il United States Patent O g HIGHLY SENSE'IIVE RELAY WITH PERMANENT Relays are already lknown which include a magnetic circuit with a permanent magnet producing a ilux across the pole-pieces and the armature which may be increased or which may be reduced to zero by a flux produced by a winding inducing a magnetomotive lforce in said magnetic circuit.

Such relays are not sensitive since the flux produced by the winding should close over the permanent magnet, the reluctance of which is high and, consequently, any modification in ilux in such a circuit requires a high number of ampere-turns; in order to increase the sensitivity of such relays, it has been proposed to provide them with a magnetic shunt constituted by a member of magnetic metal inserted between the two pole-pieces. It has also been proposed to resort to a magnetic shun-t provided with a gap. In both cases, the total flux of the permanent magnet is subdivided between the elementary circuit closed over a fraction of the pole-pieces and the shunt and that including the pole-pieces and the armature. This subdivision of the iluxes is per- `formed in relationship with the reluctances in the two circuits and it is necessary, in order to obtain a sufcient iiux in the circuit passing through the armature, -to provide a comparatively high shunt reluctance. It is therefore necessary to resort to saturated iron shunts, but, by reason of this saturation, the magnetomotive force required for the passage through said shunt of the flux produced in the armature, remains high. It has been attempted to bring a remedy to these conditions by resorting to a shunt provided with a gap. The relays obtained are much more sensitive than those provided with an iron shunt, but it has been found that it was still possible to increase their sensitivity.

As a matter of fact, it is possible to obtain the same flux in the circuit of the armature with an iron shunt having a lower reluctance, provided the flux passing through the shunt is very high, since the fluxes :are subdivided between -the two circuits in a ratio reverse of that of the reluctances. With the shunt relays of the types known hitherto, wherein the magnetic shunt circuit is closed over the pole-pieces, it is impossible to increase said total flux, since the pole-pieces of a highly magnetic metal are speedily saturated.

Our invention removes this drawback by closing the circuit of the permanent magnet over the actual shunt and by securing the pole-pieces formed by small uprights to two points of said shunt, so as to provide the magnetomotive force required `for the armature circuit.

Consequently, our improved relay includes chiefly fa permanent magnet, a magnetic circuit or shunt constituted by a member of a large cross-section extending from one pole of the magnet to the other, two pole-pieces of a highly magnetic metal secured to two points of said magnetic circuit or shunt, a winding carried by at least one of said pole-pieces and an armature cooperating with said pole-pieces.

-It has already been proposed to adjust the sensitivity of such relays provided with a magnetic shunt lby making the permanent magnet turn around the axis of symmetry of the pole-pieces, so as to make the flux induced in the magnetic circuits of the relay vary. Said adjust- ICC ment is eiicient but the induced flux varies to a substantial extent only during the fraction of a revolution during which the surface of the pole-pieces separates from the surface of the magnet. Consequently, this requires a delicate adjustment. Furthermore, it is a known tact that the maximum magnetization of a permanent magnet is retained only if its magnetic circuit is permanently closed by a magnetic circuit of a low reluctance, which is not the case with this prior arrangement. By making the permanent magnet cooperate no longer with the pole-pieces bu-t with the shunt in accordance with the invention, these drawbacks are overcome.

As a matter of fact and in accordance with a preferred embodiment'of our invention, the magnetic circuit or .shunt is constituted by a thick cylindrical dished member, of which the peripheral edge cooperates with the poles of the permanent magnet, the actual pole-pieces constituted by two small cylindrical uprights being carried by two diametrically opposed points of the dished member.

We obtain thus a shunt of a uniform cross section, whatever may be the location of the magnet revolving round its axis, -while a low constant reluctance is obtained by reason or" the excellent closure ensured by the peripheral annular' edge of the shunt, the magnetomotive force at the lower ends of the small uprights being then an accurate sinusoidal function of the angle formed by the plane passing through the axes of the uprights with the axis of the magnet poles.

It is also possible to ensure a partial or complete adjustment through a second shunt positioned on the surface of the permanent magnet opposed to the first-mentioned shunt and said second shunt -is either axially movable, so as to provide/a modication in size of the gap Separating it from the magnet, or else, it is revol-vable so as to make the area of its surface facing the magnet poles vary. Said adjustment by means of a second shunt may be associated with the adjustment provided by the rotation of the magnet, the second shunt adjusting the value of the flux in the first shunt, while the rotation of the magnet adjusts the sinusoidally varying value of the component of the magnetomotive force generating the iiux in the armature circuit.

Our invention will be better understood from the reading of Ythe following disclosure given by way of example, reference being made to the accompanying drawings, wherein:

- FIG. 1 -is a diagrammatic cross-sectional view of the relay in its open condition.

lFIG. 2 is a corresponding view with the relay in its closed condition.

FIG. 3 is a view corresponding to FIGS. 1 and 2, the relay being in the condition corresponding to the beginning of its release.

`FIG. 4 is a diagrammatic end view of the lrelay taken from the left side of FIG. 1.

FIG. 5 is a diagram showing the lvariation of the ilux in the shunt las a function of the magnetomotive yforce produced by the Winding or windings.

FIG. 6 is an axial sectional view of a iirst embodiment of the relay when complete.

FIG. 7 is an exploded view of the relay illustrated in FIG. 6, showing 4the main components thereof.

`FIG. 8 is a view corresponding to FIG. 6, of a second embodiment.

FIG. 9 is an exploded view of a modication of the section including the permanent magnet and the shunts of a third embodiment.

The relay according to our invention includes essentially a permanent magnet 1, a shunt 2 of mild magnetic steel, two small uprights 3 of a magnetic material having a high permeability, forming the pole-pieces and secured to the magnetic shunt at two potentiometrically selected points thereof, windings 4 surrounding said uprights, an armature blade 5 of a magnetic material, having a high permeability and a spring 6 exerting on the armature a force opposing magnetic attraction.

In the case illustrated in FIG. 1, the magnet I produces a fiux in the shunt 2. Considering on the shunt 2 two points N1 and S1 to which the small uprights 3 of a high grade magnetic material are secured, we will assume that for the above-described relay, the gaps formed by the armature in the relay when closed, have a width of two microns with a surface of 0.05 sq. cm. and that the induction required for obtaining the desired attractive force, adapted to hold the armature against the force exerted by the spring with a suitable margin of safety, is equal to 5,000 gauss. In such a case the flux in the circuit passing through the gaps of the armature will be 5000 0.05=250 maxwells. The magnetic permeability of the pole-pieces and of the armature being very high, it is possible to consider only the reluctance of the gaps in the circuit passing through the pole-pieces. This reluctance is 0.0004+0.05=0.008, which requires for the passage of a flux of 250 maxwells a magnetomotive force of 1.6 ampere-turns. Y When the relay isl closed, as shown in FIG. 2, the total flux of the permanent magnet is subdivided between the two circuits: the cross-section of the shunt and the magnetomotive force of the permanent magnet are selected in a manner such that the total flux pp may be equal to 2,250 maxwells, of which 2,000 maxwells forming the flux qbF-fpr, pass through the shunt between N1 and S1, while the remaining 250 maxwells forming the flux p1 pass through the armature circuit. The reluctance of the shunt between N1 and S1 should therefore be equal to:

(1,6 om 2, 1 06 maxwells and the magnetomotive force between N1 and S1 is equal to 1.685 ampere-turns.

In order to cut out completely the flux (pr, it is necessary therefore to produce in the circuit of the armature an antagonistic magnemotive force of 1.685 ampere-turns in the opposite direction. As a matter of fact, the armature circuit opens when the ux passing through the shunt between N1 and S1 has a value ranging between the two values 0 and pF-or, that is, equal to 115s with a magnetomotive force between N1 and S1 rising between 1.6 and 1.685 ampere-turns. The magnetomotive force between N1 and S1 rising from 1.6 to 1.685 ampereturns, while the magnetomotive force produced by the winding 4 rises from to 1.685 ampere-turns, the release is obtained for a number of ampere-turns in the winding 4 lying between 0 and 1.685 ampere-turns.

As a matter of fact, the reluctance of the shunt varies; the value 1.685 ampere-turns is only an approximate value and it is therefore interesting to select a shunt having a maximum permeability and to obtain a ratio p0/fpF-q5, as near unity as possible (FIG. 5).

When it is desired to adjust the relay, it is possible to make the magnetomotive force between the points N1 and S1 vary. In these previously known relays, in which the magnet was adapted to rotate, the modification in the magnetomotive force was obtained by a modification in the linx sent into the magnetic circuit, which modification CIL was produced by a reduction of the cross-section of the gap at the junction between the magnet and the magnetic fiux. In practice, such a modification is very speedy with reference to the rotation of the magnet and it is obtained suddenly, which makes the adjustment a difficult matter. With our improved relay (FIG. 4) wherein the shunt 2 is given a shape of a cylindrical cup or dished member having a broad peripheral track 7 engaged by the poles of the circular magnet 1, provided advantageously with two fiat parallel lateral surfaces 8, the total flux inside the shunt will be constant and equal to a maximum by reason of the low reluctance of the contact gaps of a large area and very reduced width. The magnetomotive force between two points of a magnetic flux being proportional to the spacing of said points measured along a line parallel with the axis of the flux, it is apparent that the electromotive force between N1 and S1 varies in the same manner as the cosine of the angle a, which is the angle of the magnetic axis of the magnet 1 with the line N1S1. The total iiux in the shunt being defined by the permanent magnet 1 and the characteristic properties of the shunt formed by the cup 2, the modification in the magnetomotive force in the armature circuit is an arcuate sinusoidal function of said angle a. If the total flux of the shunt is caused to vary in any known manner, for instance by means of a secondary shunt which deilects a fraction of the flux of the permanent magnet, the value of the magnetomotive force will be a function of said further iiux, but the rotation of the flux thus modified by the rotation of the magnet and of the secondary shunt will still provide a sinusoidal modification of the magnetomotive force.

FIGS. 6 and 7 illustrate a mechanical embodiment of the above-described relay. Said relay includes a cylindrical permanent magnet 1 with two parallel flat sides 8 along its lateral surface. As disclosed hereinafter, said magnet can revolve round a spindle of an amagnetic metal passing through an axial bore 9 in said magnet. The magnet I cooperates with a circular dished shunt 2 made of mild magnetic steel and of which the edge 7 forms an annulus bearing against the ends of the permanent magnet 1. Said dished shunt 2 is also provided with an axial bore 1li?. Its thickness is such that under the action of the flux generated by the permanent magnet, said shunt shows a maximum permeability and the magnetic ux passing through it is far from saturation ux.

The bottom of the dished shunt 2 is provided at two diametrically opposed points with bores inside which are fitted with a force fit the lower ends of two small cylindrical uprights 3 made of a highly magnetic material, that is, a material which provides a maximum permeability; in order to obtain however a sufficient induction in the gaps between the armature and the pole-pieces, the ends 11 of the uprights or pole-pieces 3 have a smaller diameter and, in order to reduce to the utmost the reluctance of the gap in front of the pole-pieces, the terminal surfaces of said pole-pieces are polished with a very high accuracy, so as to ensure a gap of only a few microns with the armature blade.

Two windings 41 are fitted over the small uprights 3 and are connected in series. They are held in position by a clamping plate 12 made of plastic material and fitted over the ends of the pole-pieces, while leaving the ends 11 of the latter free. The plate 12 clamping the windings carries two studs 13 which serve for the guiding of the armature and its outer surface is provided round the central bore 14 in the plate with an arcuate recess in which is housed the lower end of frusto-conical spiral spring 15 corresponding to the spring 6 of FIGS. 1 to 3.

The armature rod 1.6 passes coaxially through the bores 9, 10, I4 in the permanent magnet 1, the dished shunt 2 and the clamping plate i12. It carries at its end facing the ends of the pole-pieces the armature 5` made of high grade magnetic material. Its ends are provided with grooves engaged by circlip washers 17.

The relay illustrated in FIG. 8 is, for its major part, identical with that described hereinabove and the same components are designated by the same reference numbers. However, the bore 1d, in the dished shunt 2, is tapped so as to be engaged by the threaded end of a rod 18 inside the hollow shunt of which the armature rod 16 can slide freely. The bore 9 in the magnet y1 has an enlarged diameter so as to allow the passage through it of the threaded rod 13. A secondary dished shunt -19 made of mild steel, of a shape similar to that of the `shunt 2, is fitted over the bolt 18 and its peripheral upstanding ange faces the magnet 1. It is held spaced from the magnet 1 by a spring 2t) and it can be urged nearer said magnet by screwing down the threaded rod 1S. The adjustment of the gap between the magnet 1 and the secondary shunt 19 provides a modification in the absolute value of the flux produced in the primary shunt Z. The rotation of the permanent magnet 1 provides a sinusoidal modification of the magnetomotive force generated between the two uprights or pole-pieces by the fiuX of which -the value is in its turn adjusted by the shunt 19.

FIG. 9 illustrates a modification of the adjusting section which provides `the adjustment solely through rotation of a secondary shunt 21. To this end, the magnet is held fast in position by projections ZZ forming abutments on the primary shun-t 2 for the lateral flat surfaces 8 of the magnet. The secondary shunt t211 is formed by a cylindrical dished member provided withtwo flat lateral surfaces 23, so as to allow a modification in the area of the gap between the shunt 21 and the magnet 1. The secondary shunt 21 is urged towards the magnet 1 by an elastic washer 24 clamped in position by the threaded rod 1S.

The above-described embodiments, given by way of examples, may be modified in any desired manner within the scope of the accompanying claims.

What we claim is:

1. A highly sensitive relay, comprising a permanent magnet, a magnetic dished shunt including a bottom, the thickness of which is the same as that of the magnet, a thick upstanding peripheral annular wall concentrically arranged with reference 4to the magnet and on which the ends of the magnet rest, two elongated pole-pieces of a highly magnetic material rigidly secured to two diametrically opposed points of the bottom of the shunt and facing away from the magnet, a winding carried by at least one of said pole-pieces, an armature facing the outer ends of the pole-pieces, and elastic means urging the armature away from the pole-pieces.

2. A highly sensitive relay, comprising a permanent magnet, a magnetic shunt including a central part and upstanding terminal parts on which the ends of the'magnet rest, two elongated pole pieces of a highly magnetic material rigidly secured to two longitudinally spaced points of the central part of the shunt and facing away from the magnet, a winding carried by at least one of said pole-pieces, an armature facing the outer ends of the pole-pieces, and elastic means urging the armature away from the pole-pieces.

3. A highly sensitive relay, comprising a permanent magnet, a magnetic shunt including a central part the thickness of which is substantially the same as that of the magnet and upstanding terminal parts on which the ends of the magnet rest, two elongated pole-pieces of a highly magnetic material rigidly secured to two longitudina-lly spaced points of the central part of the shunt and facing away from the magnet, a winding carried by at least one of said pole-pieces, an armature facing the outer ends of the pole-pieces, and elastic means urging the armature away from the pole-pieces.

4. A highly sensitive relay comprising a permanent magnet, a magnetic dished shunt including a bottom and an upstanding peripheral annular wall concentric with the magnet and on which the ends of the magnet rest, two elongated pole-pieces of a highly magnetic material rigidly secured to two diametrically opposed points of the bottom of the shunt and facing away from the magnet, a winding carried by at least one of said pole-pieces, an armature facing the outer ends of the pole-pieces, and elastic means urging the armature away from the polepieces.

5. A highly sensitive relay comprising a permanent magnet, a magnetic dished shunt including a bottom, thickness of which is substantially the same as that of the magnet, and a thick upstanding peripheral annular wall concentric with the magnet and the periphery of which registers with the magnet poles to allow the latter to slide along said periphery, a spindle of `a non-magnetic material axially connecting said permanent magnet and said shunt so as to allow relative angular movement between the permanent magnet and the shunt, two elongated pole-pieces of a highly magnetic material rigidly secured -to two diametrically opposed points on the bottom of the shunt and facing away from the magnet, a winding carried by at least one of said poleapieces, an armature facing the outer ends of the pole-pieces, and elastic means urging the armature away from the pole-pieces.

6. A highly sensitive relay comprising a permanent magnet, a first magnetic dished shunt including a bottom and an upstanding peripheral annular wall concentric with the magnet, the periphery of said first shunt registering with the magnet poles to allow the latter to slide along said periphery, a second magnetic shunt shaped as a dished cylindrical element with two flat lateral surfaces, the parts of the upstanding annular wall of which are concentrically arranged with reference to the magnet and rest on the surface of the permanent magnet facing away from said first shunt, a spindle of a non-magnetic material axially connecting said permanent magnet and both said dished shunts while allowing the angular shifting of said second shunt relative to the permanent magnet .and of the permanent magnet relative to said first shunt, two elongated pole-pieces of a highly magnetic material secured to two diametrically opposed points on the bottom of said first shunt and facing away from the magnet, a winding carried by at least one of said pole-pieces, an armature facing the outer ends of the pole-pieces, and elastic means urging the armature away from the pole-pieces.

7. A highly sensitive relay comprising a permanent magnet, a first magnetic dished shunt including a bottom and an upstanding peripheral annular wall concentric with the magnet on which the ends of the magnet rest, a second magnetic shunt shaped as a dished cylindrical element with an upstanding annular wall concentrically arranged with reference to the magnet and facing the surface of the permanent magnet facing away from said first shunt, a spindle of a non-magnetic material axially connecting said permanent magnet and both said dished shunts, means cooperating with said spindle and said second shunt to displace said second shunt towards and away from the permanent magnet, two elongated polepieces of a highly magnetic material secured to two diametrically opposed points on the bottom of said first shunt and facing away from the magnet, a winding carried by at least one of said pole-pieces, an armature facing the outer ends of the pole-pieces, and elastic means urging the armature away from the pole-pieces.

8. A highly sensitive relay comprising a permanent magnet, a first magnetic dished shunt including a bottom and an upstanding peripheral annular wall concentric with the magnet, abutments provided in said annular wall between which the ends of the magnet rest, a second magnetic shunt shaped as a dished cylindrical element with two fiat `lateral surfaces, the parts of the upstanding annular wall of which are concentrically arranged with reference to the magnet and rest on the surface of the permanent magnet facing away from said first shunt, a spindle of a non-magnetic material axially connecting said permanent magnet and both said dished shunts while allowing the angular shifting of said second shunt relative to the permanent magnet, two elongated pole-pieces 'i S of a highly magnetic material secured to two diametrical- References Cex in the file of this patent 1y ppOSd POlIlS O11 th@ bottom Of. Sald flISt S'hllnt and facing away from tha magnet, a Wmdmg carried by at 3 1 least one of said pole-pieces, an armature facing the outer 3620135 Wllson May 4 1887 ends of the pole-pieces, and elastic means urging the 1548596 Ghegan Aug 925 

2. A HIGHLY SENSITIVE RELAY, COMPRISING A PERMANENT MAGNET, A MAGNETIC SHUNT INCLUDING A CENTRAL PART AND UPSTANDING TERMINAL PARTS ON WHICH THE ENDS OF THE MAGNET REST, TWO ELONGATED POLE PIECES OF A HIGHLY MAGNETIC MATERIAL RIGIDLY SECURED TO TWO LONGITUDINALLY SPACED POINTS OF THE CENTRAL PART OF THE SHUNT AND FACING AWAY FROM THE MAGNET, A WINDING CARRIED BY AT LEAST ONE OF SAID POLE-PIECES, AN ARMATURE FACING THE OUTER ENDS OF THE POLE-PIECES, AND ELASTIC MEANS URGING THE ARMATURE AWAY FROM THE POLE-PIECES. 